Lithium Batteries installation

[nicknorman]

21 minutes ago, IanD said:

Two can play that game -- what's Morse code for "Melted any good CANbus cables recently"? 🙂

There is no morse code for inverted commas. Or a question mark. Or a slightly smiley emoji. Nor is there any distinguishment between lower case and upper case. In fact do you know ANYTHING about morse code?

Apart from the fact that you invented it, obviously.

[Sea Dog]

10 hours ago, nicknorman said:

Apart from the fact that you invented it, obviously.

He didn't invent morse code, his...

 

da da did it

[magnetman]

12 hours ago, peterboat said:

Actually lots of modern diesels have throttles now, 

My 1960s Perkins P4 in one of the Boats has the speed controlled by a butterfly valve in the air intake. 

 

 

@Tony Brooks knows about this one I think the high pressure pump is controlled by vacuum rather than mechanically. 

 

 

 

Edited February 15 by magnetman

[IanD]

11 hours ago, nicknorman said:

There is no morse code for inverted commas. Or a question mark. Or a slightly smiley emoji. Nor is there any distinguishment between lower case and upper case. In fact do you know ANYTHING about morse code?

Apart from the fact that you invented it, obviously.

If you can't take sarcasm, don't dish it out.

 

I didn't invent Morse code, but unlike some I do at least seem able to apply Ohm's and Kirchoff's laws... 😉

Edited February 15 by IanD

[nicknorman]

42 minutes ago, IanD said:

If you can't take sarcasm, don't dish it out.

 

I didn't invent Morse code, but unlike some I do at least seem able to apply Ohm's and Kirchoff's laws... 😉

Shock horror you didn't invent it? I am amazed. Anyway as we both know Ohm's and Kirchoff's laws have long been discredited for being inaccurate.

Edited February 15 by nicknorman

[IanD]

10 minutes ago, nicknorman said:

Shock horror you didn't invent it? I am amazed. Anyway as we both know Ohm's and Kirchoff's laws have long been discredited.

Maybe that explains why you don't seem able to work out simple voltage drops and currents in connections and wires then... 😉

 

Here are two quotes; I'll leave it up to the (extremely bored by now...) reader to decide which is correct.

 

"Certainly the difference in cable sections (and hence resistance) between the battery 0v line (70mm^2) and the BMV data line (very thin) means that the dc current flowing through that thin wire, and thence through another thin wire between BMS and cell 0v, wont be much. But then again “not much” of 200A can still be a fair bit. But if you introduce some slightly corroded or bad connection in the 70mm^2 wire, you could end up with large currents flowing through the thin wires and much smoke and melting ensuing."

 

"BTW I went and looked up some actual numbers for you -- shielded data cables are recommended to be grounded at both ends so long as the voltage difference between the grounds is less than 1V rms (this is aimed at mains systems, to prevent ground loops), so they'll be perfectly happy with that and certainly not smoke or melt. If you have a 1V drop in a poor ground connection carrying 200A (5mohms -- your number not mine) then it might well burst into flames since it will dissipate 200W, but the shielded data cable (and the PCB it connects to) will still be perfectly happy, it might carry an amp or two of current down the shield -- and an unshielded one won't even notice. Numbers matter... 😉"

 

I expect this will trigger more insults/character assassination/diversion from you rather than doing what you accused me of *never* doing, which is admitting you were wrong... 😞

Edited February 15 by IanD

[Guest]

15 minutes ago, IanD said:

 

Here are two quotes; I'll leave it up to the (extremely bored by now...) reader to decide which is correct.

 

 

The thing is IanD most I would guess don't really know or in fact care who is correct. Simply because most don't have the technical knowledge to decide, this isn't the 'engineering' type forum populated by obvious geeks like you where no doubt such subjects are gone into intense detail and depth. 

 

What we do see is someone who at each and every opportunity tries to trample down somebody else's knowledge 'because IanD is the 'expert on just about bloody everything boating' THAT is what is boring. Just try for once shrugging your shoulders and saying 'ok it doesn't really matter if somebody doesn't agree with me' because in reality it simply doesn't.

 

It's an internet forum it's not a University lecture.

[nicknorman]

11 minutes ago, IanD said:

Maybe that explains why you don't seem able to work out simple voltage drops and currents in connections and wires then... 😉

 

Here are two quotes; I'll leave it up to the (extremely bored by now...) reader to decide which is correct.

 

"Certainly the difference in cable sections (and hence resistance) between the battery 0v line (70mm^2) and the BMV data line (very thin) means that the dc current flowing through that thin wire, and thence through another thin wire between BMS and cell 0v, wont be much. But then again “not much” of 200A can still be a fair bit. But if you introduce some slightly corroded or bad connection in the 70mm^2 wire, you could end up with large currents flowing through the thin wires and much smoke and melting ensuing."

 

"BTW I went and looked up some actual numbers for you -- shielded data cables are recommended to be grounded at both ends so long as the voltage difference between the grounds is less than 1V rms (this is aimed at mains systems, to prevent ground loops), so they'll be perfectly happy with that and certainly not smoke or melt. If you have a 1V drop in a poor ground connection carrying 200A (5mohms -- your number not mine) then it might well burst into flames since it will dissipate 200W, but the shielded data cable (and the PCB it connects to) will still be perfectly happy, it might carry an amp or two of current down the shield -- and an unshielded one won't even notice. Numbers matter... 😉"

 

I expect this will trigger more insults/character assassination/diversion from you rather than doing what you accused me of *never* doing, which is admitting you were wrong... 😞

 

Have you ever thought of going into politics? You certainly have the prerequisite of a selective memory.

As I explained before, if the thin wire is uniform they you are correct. But it isn't. As I explained, the "thin wire" circuit is from the shunt to the BMV, from the BMV to the BMS, and from the BMS to the cell 0v. All of which are reasonably similar and adequate cables that won't melt. However within the BMS there would be (if I hadn't designed it out) a PCB track connecting the BMV and cell 0v wires. A thin PCB track which at first glance would not be required to carry any more current than the sub-mA current arising from the TTL level 232 data lines. So likely very thin and thus concentrating nearly all the circuit resistance, and hence nearly all the heat, in a very small area with virtually zero thermal mass or ability to disspate heat. And even if the fat connection did get very hot and melt a bit, that is easily fixed. Whereas internal damage to the BMS pcb would require a new BMS.

 

And then we have the problems that you are choosing to forget - a disconnection or near disconnection of the battery -ve which would keep services live but pass all the current through the alternative route and vapourise it. And the fact that the mV accuracy of the 0v BMS line would be compromised by even relatively small currents following the alternative path.

 

All of which comes back to my point that it is bad practice to design systems that have alternative and "unintended" current paths.

 

Also important to bear in mind that FMEA is only as good as the failure modes you think of. Building in weak points/bad design even though you can't immediately think of a scenario where it might cause a problem, is still bad design. If you are a good engineer, that is.

[IanD]

20 minutes ago, nicknorman said:

 

Have you ever thought of going into politics? You certainly have the prerequisite of a selective memory.

As I explained before, if the thin wire is uniform they you are correct. But it isn't. As I explained, the "thin wire" circuit is from the shunt to the BMV, from the BMV to the BMS, and from the BMS to the cell 0v. All of which are reasonably similar and adequate cables that won't melt. However within the BMS there would be (if I hadn't designed it out) a PCB track connecting the BMV and cell 0v wires. A thin PCB track which at first glance would not be required to carry any more current than the sub-mA current arising from the TTL level 232 data lines. So likely very thin and thus concentrating nearly all the circuit resistance, and hence nearly all the heat, in a very small area with virtually zero thermal mass or ability to disspate heat. And even if the fat connection did get very hot and melt a bit, that is easily fixed. Whereas internal damage to the BMS pcb would require a new BMS.

 

And then we have the problems that you are choosing to forget - a disconnection or near disconnection of the battery -ve which would keep services live but pass all the current through the alternative route and vapourise it. And the fact that the mV accuracy of the 0v BMS line would be compromised by even relatively small currents following the alternative path.

 

All of which comes back to my point that it is bad practice to design systems that have alternative and "unintended" current paths.

 

Also important to bear in mind that FMEA is only as good as the failure modes you think of. Building in weak points/bad design even though you can't immediately think of a scenario where it might cause a problem, is still bad design. If you are a good engineer, that is.

 

Like I said, insults, diversion (ooh look, battery disconnection!), ignoring what you wrote, and a complete refusal to admit you were wrong even when it's there in black and white. Are you a Donald Trump sockpuppet?

 

If you've ever looked at actual current limits for PCB tracks, even quite a thin one will take a surprising amount of current -- a 0.6mm (0.025") track will carry 2.5A continuously and 5A shorter-term without damage. Numbers matter... 😉

 

https://www.mclpcb.com/blog/pcb-trace-width-vs-current-table/

 

P.S. If the battery ground is disconnected then you're correct, damage would occur, and this needs to be considered -- but that's not what you wrote (and I quoted to avoid doubt), is it? 🙂

 

 

Edited February 15 by IanD

[magnetman]

18 minutes ago, MJG said:

 

The thing is IanD most I would guess don't really know or in fact care who is correct. Simply because most don't have the technical knowledge to decide, this isn't the 'engineering' type forum populated by obvious geeks like you where no doubt such subjects are gone into intense detail and depth. 

 

What we do see is someone who at each and every opportunity tries to trample down somebody else's knowledge 'because IanD is the 'expert on just about bloody everything boating' THAT is what is boring. Just try for once shrugging your shoulders and saying 'ok it doesn't really matter if somebody doesn't agree with me' because in reality it simply doesn't.

 

It's an internet forum it's not a University lecture.

 

 

https://en.m.wikipedia.org/wiki/Ne_supra_crepidam

 

 

Careful now !

 

Beware of the ultracrepidarians. 

[IanD]

4 minutes ago, magnetman said:

 

 

https://en.m.wikipedia.org/wiki/Ne_supra_crepidam

 

 

Careful now !

 

Beware of the ultracrepidarians. 

 

Except that I'm quite careful not to pass judgement beyond my expertise, and unlike some people I'm happy to admit I'm wrong when I've made a mistake, because that's how you learn things, isn't it?

 

I've given up trying to convince Nasty Nick (there, a Trumpism for you!) that he's actually guilty of what you quoted, he can join MJG on the naughty step for the same reason...

[GUMPY]

9 minutes ago, IanD said:

unlike some people I'm happy to admit I'm wrong when I've made a mistake, because that's how you learn things, isn't it?

Any chance of a link, search facility is not finding anything

 

[Tacet]

11 minutes ago, IanD said:

 

Except that I'm quite careful not to pass judgement beyond my expertise, and unlike some people I'm happy to admit I'm wrong when I've made a mistake, because that's how you learn things, isn't it?

 

I've given up trying to convince Nasty Nick (there, a Trumpism for you!) that he's actually guilty of what you quoted, he can join MJG on the naughty step for the same reason...

If it helps, I can find a couple of occasions where you were wrong - but did not explicitly admit it.

[IanD]

5 minutes ago, Tacet said:

If it helps, I can find a couple of occasions where you were wrong - but did not explicitly admit it.

 

Please do***, and I will happily own up. After all, nobody's perfect... 🙂

 

Just to be fair, maybe you should extend the same offer to Nick too? There's one obvious candidate a couple of posts back 😉

 

*** (small print) Terms and conditions apply -- facts not opinions.

Edited February 15 by IanD

[Guest]

21 minutes ago, IanD said:

I've given up trying to convince Nasty Nick (there, a Trumpism for you!) that he's actually guilty of what you quoted, he can join MJG on the naughty step for the same reason...

 

Do grow up you sad little man....

 

Utterly pathetic.

[nicknorman]

I blame DMR. I was going to let it drop because there is no point in arguing with a narcissist, but then Dave came along and drew some parallel with Gibbo, so I felt morally obliged to continue.

[Alan de Enfield]

55 minutes ago, MJG said:

What we do see is someone who at each and every opportunity tries to trample down somebody else's knowledge 'because IanD is the 'expert on just about bloody everything boating'

 

C'mon, be fair its not just boats - you forgot, satellites, telephones, WiFi, antennas, electric vehicles, cycling, & anything electronic.

[Guest]

Just now, Alan de Enfield said:

 

C'mon, be fair its not just boats - you forgot, satellites, telephones, WiFi, antennas, electric vehicles, cycling, & anything electronic.

 

Ah yes my bad, sorry for the omission's.

 

I suspect you will shortly be joining Petulant Pat Pending's so called 'naughty step' if you are not careful.

 

PS except you forgot 'wood burning stoves' as did I.

[Alan de Enfield]

1 minute ago, MJG said:

 

Ah yes my bad, sorry for the omission's.

 

I suspect you will shortly be joining Petulant Pat Pending's so called 'naughty step' if you are not careful.

 

 

[IanD]

17 minutes ago, Alan de Enfield said:

 

C'mon, be fair its not just boats - you forgot, satellites, telephones, WiFi, antennas, electric vehicles, cycling, & anything electronic.

 

Yeah, true, only things I know about in some depth... 😉

 

(which admittedly excludes quite a lot on boats...)

 

Having said that, I believe you're the resident expert on many things too -- anchors, ropes, engines, mooring, hulls, anything legal, CART regulations, caravan parks, towing things with cars, why EVs are bad, BW/CART financing -- and are not exactly shy to correct people on any of these matters either... 😉

Edited February 15 by IanD

[Guest]

Just now, IanD said:

 

Yeah, true, only things I know about... 😉

 

(which excludes quite a lot on boats...)

 

Having said that, I believe you're the resident expert on many things too -- anchors, ropes, engines, mooring, hulls, anything legal, CART regulations, caravan parks, towing things with cars, why EVs are bad, BW/CART financing -- and are not exactly shy to correct people on any of these matters either... 😉

 

The key difference, that you seem to be missing, is that most on here will give it a couple of goes with their posts and then realise some things are just not worth persisting with, especially if you are part of the discussion.

 

Where as you go on and on and on and on and on and on until you grind people down leaving you with the last word giving the impression that you have 'won' the argument. Or you play the victim and cry about ad hominem attacks (which you yourself do a fair few of)

 

Most have you sussed now though.

[dmr]

1 hour ago, nicknorman said:

I blame DMR. I was going to let it drop because there is no point in arguing with a narcissist, but then Dave came along and drew some parallel with Gibbo, so I felt morally obliged to continue.

 

Yes, this thread (argument) has got better, I think maybe 7/10 for you 😀

Can you say a bit more about the errors in Ohms Law? (or probably best not).

[Iain_S]

15 hours ago, nicknorman said:

There is no morse code for inverted commas. Or a question mark. Or a slightly smiley emoji. (snip)

.-..-.   ..--..  ---... -....- -.--.-

[Nightwatch]

5 hours ago, Sea Dog said:

He didn't invent morse code, his...

 

da da did it

Very good.

[nicknorman]

1 hour ago, dmr said:

 

Yes, this thread (argument) has got better, I think maybe 7/10 for you 😀

Can you say a bit more about the errors in Ohms Law? (or probably best not).

Yes. Apply some voltage to a resistor, what is the instantaneous current? You can’t work it out using ohms law because it varies. Shot noise. And thermal noise.  So yes ohms law kind of works in an imprecise way at a cursory glance, but in a detailed way it doesn’t work.

Then there is quantum tunnelling.